BufferedInputStream

A BufferedInputStream adds
functionality to another input stream-namely,
the ability to buffer the input and to
support the mark and reset
methods. When the BufferedInputStream
is created, an internal buffer array is
created. As bytes from the stream are read
or skipped, the internal buffer is refilled
as necessary from the contained input stream,
many bytes at a time. The mark
operation remembers a point in the input
stream and the reset operation
causes all the bytes read since the most
recent mark operation to be
reread before new bytes are taken from
the contained input stream.

Causes the current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object, or
some other thread interrupts the current thread, or a certain
amount of real time has elapsed.

count

The index one greater than the index of the last valid byte in
the buffer.
This value is always
in the range 0 through buf.length;
elements buf[0] through buf[count-1]
contain buffered input data obtained
from the underlying input stream.

marklimit

The maximum read ahead allowed after a call to the
mark method before subsequent calls to the
reset method fail.
Whenever the difference between pos
and markpos exceeds marklimit,
then the mark may be dropped by setting
markpos to -1.

markpos

The value of the pos field at the time the last
mark method was called.

This value is always
in the range -1 through pos.
If there is no marked position in the input
stream, this field is -1. If
there is a marked position in the input
stream, then buf[markpos]
is the first byte to be supplied as input
after a reset operation. If
markpos is not -1,
then all bytes from positions buf[markpos]
through buf[pos-1] must remain
in the buffer array (though they may be
moved to another place in the buffer array,
with suitable adjustments to the values
of count, pos,
and markpos); they may not
be discarded unless and until the difference
between pos and markpos
exceeds marklimit.

pos

The current position in the buffer. This is the index of the next
character to be read from the buf array.

This value is always in the range 0
through count. If it is less
than count, then buf[pos]
is the next byte to be supplied as input;
if it is equal to count, then
the next read or skip
operation will require more bytes to be
read from the contained input stream.

Public methods

available

Returns an estimate of the number of bytes that can be read (or
skipped over) from this input stream without blocking by the next
invocation of a method for this input stream. The next invocation might be
the same thread or another thread. A single read or skip of this
many bytes will not block, but may read or skip fewer bytes.

This method returns the sum of the number of bytes remaining to be read in
the buffer (count - pos) and the result of calling the
in.available().

Returns

int

an estimate of the number of bytes that can be read (or skipped
over) from this input stream without blocking.

close

Closes this input stream and releases any system resources
associated with the stream.
Once the stream has been closed, further read(), available(), reset(),
or skip() invocations will throw an IOException.
Closing a previously closed stream has no effect.

read

Reads bytes from this byte-input stream into the specified byte array,
starting at the given offset.

This method implements the general contract of the corresponding
read method of
the InputStream class. As an additional
convenience, it attempts to read as many bytes as possible by repeatedly
invoking the read method of the underlying stream. This
iterated read continues until one of the following
conditions becomes true:

The specified number of bytes have been read,

The read method of the underlying stream returns
-1, indicating end-of-file, or

The available method of the underlying stream
returns zero, indicating that further input requests would block.

If the first read on the underlying stream returns
-1 to indicate end-of-file then this method returns
-1. Otherwise this method returns the number of bytes
actually read.

Subclasses of this class are encouraged, but not required, to
attempt to read as many bytes as possible in the same fashion.

Parameters

b

byte: destination buffer.

off

int: offset at which to start storing bytes.

len

int: maximum number of bytes to read.

Returns

int

the number of bytes read, or -1 if the end of
the stream has been reached.